a guy who is less likly to score than you so he metiphorically 'latches onto your balls' in the hope that he can get some pussy off of your hard work and efforts.
If your mate the 'nut hugger' follows you around all night 'hugging your nuts' and laughs at all your jokes and makes you out to be the best thing going, increasing your pulling chances. Then when you have scored a chick and he hasnt, he will cause a distraction last miniute which will allow him to get the telephone number or take her or take her home instead of you.
note:all other definitions are wrong. (nut huggers) are tight underwear sometimes speedo-like. that suck your nuts (testicles) into your stomach thus heating them and lowering spemcount. sometimes tighty whites (in briefs form) can be nuthuggers
"dude i was in the locker room and i saw some one wearin some tight ass draws i mean they were tight"
" ya man i saw those. them is some nut huggers. dude needs to let them jewels cool off"